Lahore, March 8 (IANS) Eight people were killed and 45 injured Monday when a suicide bomber struck at a building housing an investigative agency in this Pakistani city, police said.

The Federal Investigation Agency (FIA) building, located in the upmarket residential Model Town neighbourhood, was teeming with employees when the massive bombing took place.

"It was a car bombing. The terrorists detonated the explosive-laden vehicle at the main gate of the building," DPA quoted Tariq Saleem Dogar, the police chief for Punjab province, as saying.

Pervez Rathor, the Lahore police chief, said eight people had died while over 45 were injured.

He said 40 to 50 people were inside the building when the suicide attack took place.

Earlier reports had said that a security guard stopped a man entering the building located in Model Town area, but the bomber blew himself up.

District Coordination Officer Sajjad Bhutta said at least 600-kg explosives had been used in the blast, Geo TV reported.

A police official said the secret agency was working in a residential area as there was shortage of offices.

The blast targeted the special investigation unit of the secret agency.

The deafening blast was so powerful that it created a huge crater and damaged buildings located close by.

An eyewitness said he could watch smoke billowing from the blast site.